How to change Java-based configuration in tests for Spring-boot based application?

Question

I'm trying to figure out how to test my code in a proper way and stuck somewhere in the middle.

What I use:

Spring-boot based Java web-application. Java based configuration. Test.

What I want:

I want to manage my testing in a proper way. I have a @RestController annotated class what has two objects what I'd like to change in tests. It's an entities provider class BooksService and database configuration class DBConfig . I want to change implementations for these classes in my tests in a simple and proper way. I don't know how to do it correctly.

What kind of help I need:

• Working project that implements this approach is most preferable. Don't spend too many words, the working code is the best way to understand it for me.
• If there is no a complete project there, so code snippets with descriptions will be useful too.
• Links to some good and simple tutorials about 1) Java based configurations 2) Replacing Java based configuration for tests.

Sorry if my thoughts are little bit messy, I'm pretty new in Java EE development and still didn't figure out with all basic topics well.

EDIT:

Here is some code

DemoApplication class

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

BooksController controller class

@RestController
public class BooksController {

    @Autowired
    BooksProvider booksProvider;

    @CrossOrigin
    @RequestMapping("/books")
    String allBooks() throws Exception {

        return this.booksProvider.fetchAllBooksAsTring();
    }

}

BooksProvider service class

public class BooksProvider {

    public String fetchAllBooksAsTring() {
        return "[\"Marting Iden\", \"Capital\", \"Strong Wind\"]";
    }
}

SimpleConfiguration configuration class

@Configuration
public class SimpleConfiguration {

    @Bean
    public BooksProvider booksProvider() {
        return new BooksProvider();
    }

}

Answer 1

In Spring Boot 1.3.x I have successfully used the following approach:

@RunWith(SpringJUnit4ClassRunner.class)
@SpringApplicationConfiguration({Application.class, IntegrationTestsConfiguration.class})
@ActiveProfiles({"it"})
@DirtiesContext(classMode = AFTER_EACH_TEST_METHOD)
public class MyIT {
    // tests 
}

as you can see apart from Application.class (the one annotated with @SpringBootApplication ) there is IntergrationTestsConfiguration.class present in @SpringApplicationConfguration . This class is responsible for overwriting beans which behaviour I wanted to change for test purposes.

This is how such class can look like:

@Configuration
public class IntegrationTestsConfiguration {

    @Bean
    @Primary
    public BooksProvider booksProvider() {
        // your custom instantiation code goes here
    }
}

In other words I have used "Primary beans approach".

Since Spring Boot 1.4.x there is @MockBean annotation available, until now I hadn't opportunity to use it but for sure it is worth checking out.

Further reading:

• Overriding an Autowired Bean in Unit Tests
• Overriding beans in Integration tests
• https://dzone.com/articles/mockbean-spring-boots-missing-ingredient

Answer 2

Take a look in the Spring Boot test. There is a very nice tutorial how to test your controllers:

https://spring.io/guides/gs/testing-web/